I am getting the error message "Serial has reached themaximum number of activations. Disable existing activations to reuse thisserial key"

I have recently updated to Windows 10 and I am now getting the error message: "There was a problem validating the license because the operating system identification seems to have changed"

Cause

If you are receiving the error, "Your serial number is invalid," or "Serial has reached the maximum number of activations. Disable existing activations to reuse this serial key":

This means you have reached the activation limit for your license and you would need to return activation's on the license to your online account.

Each Standard Unity license allows a single person to use Unity on twomachines that they have exclusive use of.

Each Student of Faculty Educational Unity license allows a single person to use Unity on one machine that they have exclusive use of.

If you are receiving the error, "There was a problem validating the license because the operating system identification seems to have changed":

If you have migrated to another machine, re-imaged your current machine, or your machine has malfunctioned and you have not returned activations on your license, you will receive an error when you try to activate Unity. If this happens, you will need to contact Support to reset your activations manually.

Resolution

To return activations on your license purchased before June 2016, go here.

To return activations on licenses purchase after June 2016, please see this article.

If you are unable to return activations on your license via the Web Store, contact support with the following information: